The embodiments herein generally relate to starter air valves used to start gas turbine engines and more specifically, the manual overrides for the starter air valve.
Many relatively large gas turbine engines, including turbofan engines, may use an air turbine starter (ATS) to initiate gas turbine engine rotation. The ATS is typically mounted on the accessory gearbox which, in turn, is mounted on the engine or airframe. Consequently, the ATS is installed in the aircraft at all times even though active operation may occur only for a minute or so at the beginning of each flight cycle, along with occasional operation during engine maintenance activities.
The ATS generally includes a turbine section coupled to an output section within a housing. The turbine section is coupled to a high pressure fluid source, such as compressed air, to drive the output section through a gear system. Thus, when the high pressure fluid source impinges upon the turbine section, the output section powers the gas turbine engine.
When the gas turbine engine of an airplane has been shut off for example, after the airplane has landed at an airport, the engine is hot and due to heat rise, the upper portions of the engine will be hotter than lower portions of the engine. When this occurs thermal expansion may cause deflection of components of the engine which can result in a “bowed rotor” condition. If a gas turbine engine is in such a bowed rotor condition, it is undesirable to restart or start the engine. One approach to mitigating a bowed rotor condition is to use the ATS to drive rotation (i.e., cool-down motoring) of a spool within the engine for an extended period of time at a selected speed and is referred to as Bowed Rotor Motoring (BRM). Enhancements to improve the efficiency of BRM are greatly desired.